Chris Cornell's Family Is Suing His Doctor Over His Death By…

Following Chris Cornell‘s death in May 2017, which was ruled a suicide by hanging, his family is taking legal action against his doctor, whom they allege harmed Cornell’s mental health.

The singer’s widow, Vicky Cornell, and her two minor children, Christopher, 12, and Toni, 14, filed the documents in L.A. Superior Court on Thursday. (Cornell was also father to 18-year-old Lillian from his previous marriage.)

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According to the lawsuit obtained by PEOPLE, Dr. Robert Koblin allegedly “negligently and repeatedly [prescribed] mind-altering and controlled substances” starting in September 2015. The drugs listed in the documents include lorazepam, for anxiety, and oxycodone, for moderate to severe pain.

Chris Cornell and his wife Vicky

Trae Patton/NBC/NBCU Photo Bank

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The documents further allege that Koblin was aware of the Soundgarden frontman’s substance abuse problems and that he wrote the prescriptions without medically examining his patient or checking on how Cornell was responding to the dosage. It also states that the drugs “clouded [Cornell’s] judgment and caused him to engage in dangerous, impulsive behaviors that he was unable to control, which cost him his life.”

Cornell was found dead at MGM Grand Detroit on May 18, 2017, hours after his most recent band, Audioslave, performed at the Fox Theatre, his rep and Detroit police told PEOPLE at the time. He was 52.

Chris Cornell with family

Paul Zimmerman/Getty

“Chris Cornell passed away late Wednesday night in Detroit, Michigan,” said his rep in a statement at the time. “His wife Vicky and family were shocked to learn of his sudden and unexpected passing, and they will be working closely with the medical examiner to determine the cause. They would like to thank his fans for their continuous love and loyalty and ask that their privacy be respected at this time.”

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Detroit police spokesperson Michael Woody told Billboard at the time that officers found Cornell laying in his hotel bathroom unresponsive after receiving a 911 call at midnight Thursday morning from an unnamed person. Local news station WXYZ reported that Cornell’s wife had called a family friend and asked him to check on her husband’s well-being.

In the weeks following the rocker’s death, Cornell’s family said they didn’t believe him to be suicidal and believed the prescription drugs found in his system may have impacted his mental state.

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Eddie Vedder of Pearl Jam and Chris Cornell

The family source told PEOPLE that on May 4 — just two weeks before Cornell’s death — he pushed his flight from Atlanta, Georgia, back a day over safety concerns about flying in inclement weather.

The next week, on May 9, Cornell made a similar choice after hearing his flight from Tuscaloosa, Alabama, was delayed due to mechanical issues. The source says that Cornell was nervous to fly due to potential plane issues, and instead drove a rental car over seven and a half hours to his intended destination.

“Clearly someone who was so hesitant and fearful to fly in these situations valued their life,” says the source. “These are not indications of someone with no regard to their well-being.”

RELATED: Chris Cornell’s Widow Vicky Opens Up About His Addiction Battle and Final Night: ‘He Didn’t Want to Die’

Opening up to PEOPLE about her late husband in June 2017, Vicky said she tried not to blame herself for her husband’s death.

“My Chris was happy, loving, caring and warm,” she told PEOPLE. “This was not a depressed man—it wasn’t like I missed that. What I missed were the signs of addiction. That disease can take over you and has full power. I’m going to do everything in my power to make sure other children don’t have to cry like mine have cried.”